Field of the Invention
The present invention relates to an image forming device, an image forming system, an image detecting unit correcting method, and an image detecting device capable of detecting an image formed on transfer paper.
Description of the Related Art
An image is formed on transfer paper by an image forming unit based on image data in an image forming device such as a copying machine, a facsimile machine, a printer, a complex machine. The image is formed based on the image data according to a set image forming condition (image forming position, color, density and the like). The image forming condition might temporarily or gradually change according to operation of the image forming device, so that a quality is maintained by various types of automatic adjusting operation.
For example, an image patch and the like is formed on the transfer paper every predetermined time in which the image forming device operates or every predetermined number of printed sheets, this is read by a line sensor and the like and a state of the image and the image forming condition are compared to each other, and it is determined whether the image is appropriately formed. When the image is not correctly formed according to the image forming condition and displacement is generated, the quality of the image is maintained by correction of the image forming condition and the like.
JP 2003-131538 A suggests the image forming device provided with density detecting unit which detects density of a toner image while a transfer material is conveyed. In this device, a conveying speed of the transfer material is changed between normal image formation and toner image density detection, so that strength of the transfer material is stabilized, a distance between the density detecting unit and paper is always constant, and density detection accuracy is improved.
However, JP 2003-131538 A has a problem that the conveying speed of the transfer material is decreased when the density is detected, so that productivity is deteriorated.
A line sensor obtained by using a CCD, a CIS and the like is generally used as the sensor which detects the image density. The line sensor is suitable for high-speed reading and this may read the transfer paper on which fixing is performed at the conveying speed of a fixing unit to confirm color reproducibility and inspect a printing position. However, the line sensor is not excellent in color reproducibility, so that there is a problem that the image is not sufficiently detected, JP 2003-131538 A also has the similar problem. Therefore, a periodic correction by a spectral colorimeter and the like of which colorimetric accuracy is assured is considered.
When the line sensor is corrected by the spectral colorimeter in a configuration in which the spectral colorimeter and the line sensor are located on the same conveying path, it is required to read the patch on the same chart; however, optimal transfer paper conveying speeds are different between the line sensor and the spectral colorimeter. In general, the transfer paper is read at a higher conveying speed by the line sensor than the spectral colorimeter. It is required to make an integrated light amount per patch constant in the spectral colorimeter, so that it is required to make a patch length longer when the patch is read at the same conveying speed as that of the line sensor. However, when the patch length is made longer, the number of charts required for correction becomes larger and there is a problem that the number of sheets to be wasted in one correction becomes larger.